Obscura Society LA: Moon Rocks - Atlas Obscura

Agua Dulce, CA

Obscura Society LA: Moon Rocks

Join the Obscura Society LA and geologist Eric Kleinsasser as we discover moon rocks, without traveling 240,000 miles through space.

The San Gabriels are one of the few locations on the Earth where anorthosite outcrops can be found, the same rocks that create the light colored areas on the Moon.

On October 10th, 2014, President Obama designated the San Gabriel Mountains a National Monument. Discover the treasures of our new permanently protected land and learn about our local geology! Beginning at the Vasquez Rocks, we will wind our way through the mountains on a geological caravan adventure that includes five stops and a short hike.


  • Vasquez Rocks: This spectacular basin is excellent visual evidence of the heavy faulting for which Southern California is famous.
  • Lamont Odett Vista Point: Overlooking Lake Palmdale, a major sag-pond created by the San Andreas Fault.
  • Monte Cristo Campground: This is the first up-close glimpse we'll get of the SGM anorthosite complex, i.e., “moon rocks.”
  • Big Tujunga Canyon Rd., road-cut of anorthositic soil: This will be a quick stop to look at a beautiful exposure of actively weathering anorthosite.
  • Eaton Saddle: A short hike overlooking the LA Basin.
  • Mendenhall Gneiss: U-Pb-Th dating of zircon grains in these gneisses puts their age at around 1.2 billion years! (reference: Silver et al. 1963, Geology, "Age Determinations in the Western San Gabriel Mountains, CA")

Kleinsasser is a PhD student in USC Earth Sciences' Geochemistry group.  His current research is aimed at investigating the weathering kinetics of silicate mineral surfaces, particularly on feldspars.  

Notes for this adventure:

  • We will email out exact meeting location to all attendees closer to the event date.
  • START AND END POINT: The tour starts at the Vasquez Rocks located about an hour from downtown LA. We will exit the San Gabriels via the Angeles Crest Highway, leaving you in La Cañada Flintridge.
  • CARPOOLING: We will be traveling as a caravan. If you’re coming as a group, we HIGHLY recommend you carpool. If you don’t have a car or are attending alone, no problem! Two weeks prior to the event you will receive an email with the carpool meet-up location near downtown LA. The carpooling meet-up time is 9:00 am.
  • WEATHER CANCELLATION: This event it weather dependent. Many of these roads tend not to be safe during rain and immediately after because of washouts or the danger of flash floods. If we are expecting significant rain on this date, we will cancel the event via email. Tickets will be refunded or transferred to a rescheduled date, depending on your availability. 
  • Arrive with a full tank of gas! There will be no where to stop for gas along the way.
  • We will be hiking! The total distance is approximately three miles, including a section with a steep incline. Please plan accordingly with water, snacks, proper shoes, and sun protection (sunscreen, hat, sunglasses, etc.).

For more information about the history of the San Gabiel Mountains and their recent designation as a National Monument, check out KCET’s article The San Gabriels: A Historical Guide to America's Newest National Monument

All ticket sales are final.